ANDROID: dma-buf: Export debugfs_list_mutex and debugfs_list

Export debugfs_list_mutex and debugfs_list to be used by other
modules for collecting dmabuf debug info.

Bug: 394900912
Bug: 267250898
Change-Id: Ie24788fcf9cf0a49316cb871dcb9191e8084ccde
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>
Signed-off-by: Jaskaran Singh <quic_jasksing@quicinc.com>
Signed-off-by: Oreoluwa Babatunde <quic_obabatun@quicinc.com>